This invention relates to a method for the separation and recovery of palladium and technetium from aqueous solutions. More specifically, this invention relates to a method for the separation and recovery of fission produced palladium and technetium from aqueous acid nuclear fuel reprocessing waste solutions.
Fission products which result from the irradiation of nuclear reactor fuels are generally considered as harmful radioactive waste which require storage in an insoluble form for centuries. Most of these waste contain metals such as palladium which, when considered in the context of an ever increasing demand for the metal and its finite and diminishing reserves, become potential resources.
The use of a platinum metals based catalyst system by United States car manufacturers has resulted in an increased demand for metals of this type. Although present systems for air pollution control are platinum based, the next generation of pollution control systems is presently scheduled to include palladium metal. Palladium has found general use as an electrical contact metal and as a catalyst for various chemical manufacture and purification processes.
Technetium is nonexistent in nature and may have properties of value which warrant its recovery. Furthermore, recovery of technetium from the waste would eliminate one more radioactive component for which long-term storage must be provided. Furthermore, since it has been found that technetium has a tendency to migrate in soil, should it be leached from the stored radioactive solid wastes, it is preferred that it be separated from the other radioactive wastes and handled separately in order to prevent this from occurring.
Technetium is present in fission product wastes as .sup.99 Tc. Palladium is present as stable isotopes containing about 15 atom percent .sup.107 Pd of long half-life but low energy (.about.0.04 Mev). This low-energy radiation together with the biological inertness of palladium suggest this material can be utilized in many applications without regard to the presence of .sup.107 Pd, such as a catalyst.
While several processes have been developed for the recovery of palladium and technetium values, none of them have been completely satisfactory, in that the character of the feed solution must be changed greatly, the selective halogenation of certain elements is required, or large quantities of radioactive wastes are generated, which must ultimately be disposed of in some manner.